1 Set the oven at 200 Celsius/gas 6. Put an upturned baking sheet in the oven. Bring a medium pan of water to the boil. Trim the asparagus, then cut each spear into three short lengths. Drop the asparagus into the pan and let it boil for two minutes, before lifting out with a draining spoon and refreshing in iced water.
2 Roll the pastry out to a rectangle measuring 34cm by 22cm. Cut the rectangle into six equal squares. Place the squares on a lined baking sheet. Using the tip of a knife, score a smaller square 1cm in from the edges of each piece of pastry. Brush a little beaten egg around the outside square of each piece of pastry.
3 Drain the asparagus on kitchen paper. Crush the goat's cheese with a fork and fold in the cream cheese and thyme. Divide the mixture between the six squares of pastry and put four asparagus pieces on each. Put the baking sheet on top of the preheated sheet already in the oven, and bake for 25 to 30 minutes, until the tarts are golden. Eat immediately.